Ceramic separators for primary batteries



Feb. 13, 1962 R. D. JAcKEL CERAMIC SEPARATORS FOR PRIMARY BATTERIES Filed April 2l, 1960 I4 FIG'. 2.

' 3,021,379 CERAMIC SEPARATORS EGR PRIMARY BATTERES Roland D. Jackel, 3110 19th St. NW., Washington, D.C. Fired Apr. 21, 1960, ser. No. 23,859

6 Claims. (Cl. 136-145)` (Granted under Title 35, U.S. Code (1952), sec. 266) This invention may be manufactured and used by or for the Government of the United States for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to separative diaphragms or separators for electrolytic cells and particularly to the production of a porous composite ceramic separator adapted for use in primary batteries of the fuel combustion type.

In the newer type of primary cells now being developed, the operating criteria for the materials used in separating the active materials from each other and in withstanding the more powerful electrolytes now in use has steadily increased. The physical, chemical, and electrical properties essential for the optimum separator or diaphragm are (l) a degree of mechanical rigidity; (2) dimensional stability; (3) a certain degree of flexibility; (4) porosity of such microscopic dimensions as to pre- Vvent migration of sediment from the active materials,

thus preventing short circuits, and (5) a high degree of resistance to attack from the more powerful chemicals and substances being utilized in modern high performance primary cells.

Other important factors involved in the choice and development of such separanve diaphragms are found in the principles of operation of the new type primary cells. Here, a gas, such as chlorine, bromine, iodine, or a mixture of these elements, may be used for the consumable cathode element in conjunction with an aqueous electrolyte and a consumable metal anode which may be of aluminum, magnesium, zinc, iron, or alloys of these metals.` Since the gases are usually introduced under pressure and flow through the closed cell and since the electrolyte is circulated externally of the cell for theremoval of waste products and heat, obviously the separators undergo mechanical and chemical stresses heretofore unknown.

Another important factor relating to the mechanical strength and dimensional stability of the separator is found in the desirability of keeping the cell elements, e.g., metal anode and carbon or other inert material diffuser, under a positive mechanical force to maintain element spacings constant as the anode is consumed. This rel quirement, which is essential to the development of large capacity primary batteries of this general type, obviously demands separator material which can withstand a considerable degree of compression while still maintaining dimensional stability. Related to the foregoing requirement is the additional element of overall area. YIn large capacity cells, the electrolyte elements may have considerable area in the nature of several square feet. 0bviously, the area of the separator must conform thereto. The problem of supplying a separator having suicient area and yet being thin and strong enough to properly perform electrochemically has been one of the stumbling blocks in the development of these high capacity primary sources of electromotive force.

United States Patent 0 ice Previously known materials such as wood, rubber, earthenware, diatomaceous earth, plastics, rubber or plastic covered wire meshes, glass wool or cloth'or other synthetic fibers have been found unsuitable. Separators made of these materials, particularly those with the larger areas, have been found to fail either mechanically or by chemical corrosion.

The principal object of my invention, therefore, is to provide a separator or separative diaphragm for use in a fuel combustion type of primary source of electromotive force which is subject to none of the disadvantages of those materials previously used in secondary type cells.

A further object of my invention is to provide a ceramic separator unit or tile which may be assembled into a separative diaphragm having considerable mechanical strength and dimensional stability for use in primary batteries.

Another object of my invention is to provide a permeable ceramic separator for primary sources of electromotive force which is liexible and has a proper degree of porosity to pass the electrolytic fluids but will prevent migration of sediment from the active materials.

Still another object of my invention is to provide a method of production of ceramic separators for use in primary batteries which separators have the required mechanical strength, dimensional stability, porosity, and resistance to chemicaland duid corrosion for such use.

Other objects and advantages of my invention will become more apparent in connection with the following description and drawings wherein:

FIGURE l is an elevation of the basic ceramic separator unit;

FIG. 2 is a plan view of the unit;

FIG. 3 is an elevation of the assembled separator; and

FIG. 4 is a cross-sectional View taken on the line 4-4 of FIG. 3.

With reference .to FIGS. l and 2, the basic separator unit or tile 16 is made as will be more fully described hereinafter. After production, horizontal and vertical holes 12 and 14 are drilled, or otherwise formed, from one edge to the other on the horizontal and vertical axes. These holes are further centrally disposed with relation to the faces 15 and 16 of the ceramic separator unit. While the dimensions of this basic unit are not necessarily limited to any particular Value, it has been found that a practical size is approximately one inch square by oneeighth inch thick. The holes may be one-sixteenth to three-thirty seconds inches in diameter.

As shown in FIGS. 3 and 4, after the basic porous ceramic separator unit 10 is produced and formed, the complete separator 29 may be formed by laying the required number of basic units in contiguous relationship and then threading through the aligned vertical and horizontal holes a thread or thin filament 22 of a suitable plastic material such as Dynel or Saran. These plastic materials have been found to possess suicient chemical stability to be so used in the presence of chlorine or other of the halogeus and concentrated electrolytes such as aqueous solutions of the halides of the anode metals. These laments 22 are knotted, as at 23, at the edges, horizontal and vertical, of the separator 2t) in order to retain the basic units in place. As will be apparent, this mode of construction provides a complete separator that has mechanical strength and dimensional stability but is yet 'elernent.

suicientlyflexible to allow for variations in the surfaces A Yare `slowly. added.k After the above listed materials are carefully mulled' so that the hydrocarbon emulsion'and corn b'iderare' thoroughly and completely distributed?V throughoutthe` body of the mix, the resultant emulsiondahipe'netljpowder is pressed' into flat tiles'or basic units df the sizeV previously mentioned, i.e., l x l x 1/s inch. The't'iles or' basicV unitsare then tiredV at a temperature of ,225,0 F. for a period of nine hours. By proper control 'f thef quantity and quality of thehhydrocarbon emulsion,

the mesh of the' corn binder, ie., its particle size, the pressure applied inv pressing the tiles or basic units to shape and thickness, and theV firing temperatures and times, theporosity and permeability of the ceramic unit can be controlled within satisfactory limits for the application'rherein described.

After theA tiles or basic separator unitare formed as described above, the holes 12 and 14 are drilled, preferably with a diamond drill of the desired diameter. The basic unitsA are then strung together, horizontally and `vertically,,and the entire separator is thus assembled. Since the joining filaments 22 are slightly elastic, care in forming the knot 23 will insure that the filaments are under aY slight tension and therefore the adjacent units will be held tightly together. In certain circumstances,

the edges of the basic units Ymay ground so as to effect a vclose union and prevent undesired lleakage at the joints.

While 'the preferred composition of themix from which the porous ceramic basic separator units are formed has beendescribed above, the talc component may be replaced by alumina, zirconia, berylli'a, and other fllermaterialsY which have a high electrical-'resistivity combined 4with 'a high degree of chemical inertness.

varying the qualities and quantities of the various components of the mix, other than the high temperature ceramic clay binder, l `may fabricate a wide variety of porous, permeable ceramic tiles or basic separator units fr'assembly into largearea separators vfor use inprimary celis which depend upon the ow of chlorine or other 'halogen gas as'an oxidizer anda material such'as hydro- 'gen,jmagnesium, aluminum, zinc, or iron forthe reducing I Whilejthe preferred forrn'and composition of/my imv'proved permeable separatorihas been described and shown YAYabove, many modifications, other'than those previously 'A mentioned, mayV suggestl themselves to those skilled in the Vfait. AV further modification might-consist offorming the`l "holes'lZ' 'and '1'4 during the pressing operation rather than "drilling, (Due tothethinness of the material, however, ""suchproce'dure'has not been altogether satisfactoryand the results have not -beensufciently uniform to-warrant present replacement of the drilling method. Itis intended, however, that allV such modifications will vfall within the y',sp'irit of kthe `invention and the scope of the appended vclaims'whe'r'ein I'claim: Y l. The method of fabricating a basic porous separator l unit for assembly Vinto a large area separator adaptedV for `insertion between the active elements of a fuel combustion Vtype of primary battery comprising:

intimatelyY dry mixing 8O parts by weight of nely Vground talc, ll() parts by weight of powdered barium carbonate and 10 parts by weight of ceramic clay;

" slowly adding 11A.V parts by weight of an hydrocarbon emulsion and 11/2 parts by weight'of a corn binder to said dry mix until said emulsion and said corn binder'are completely distributed throughout-thesaid 'dry Thus, by Y pressing the emulsion dampened mix into thin flat rectangular tiles;

firing said tiles at a temperature of 2250 F. for a period of nine hours; and

drilling holes in said fired ceramic tiles, said holes being coaxial with the vertical and horizontal axes of said thin rectangular tile where said axes are parallel to the rectangular faces of said tile.

2. A basic separator unit for assembly into a large area separator adapted for insertion between the active elements of a fuel combustion type of primary electric battery comprising a thin parallelepiped having two principal faces in the form of rectangular parallelograms and four thin edges `also in the form of rectangular parallelograms, said parallelepiped being composed of parts by weight of talc, l0 parts by weight of barium carbonate, l0 parts by 'weight of ceramic clay, 11/2 parts by weight of an hydrocarbon emulsion and l1/2 parts by weight of suitably mesh graded corn meal and having two apertures formed therein, said apertures being coaxial with those axes of the parallel'epiped which are perpendicular to the opposed edges thereof and parallel to the principal faces thereof; each of said apertures extending from one opposed edge to the other opposed edge, and said apertures intersecting each other on the third axis of said parallelepiped, which third axis is perpendicular to the, prinipal faces and parallel to the four thin edges thereof.

3. A basic separator unit for assembly into a large area separator diaphragm adapted for insertion between the active elements of a fuel combustion type of primary electric battery comprising a thin flat rectangular tile having two comparatively large rectangular face surfaces and four comparatively small rectangular edge surfaces and consisting of 80 parts by weight of talc, l0 parts by weight of barium carbonate, 10 parts by weight of ceramic cla ll/z parts by weight of an hydrocarbon emulsion, and 11/2 .parts by weight of graded corn meal, lsaid tile being provided with ltwo apertures coaxial and coext'e'nsive with those tile Vaxes `parallel to ,the facezsurfacesthereof. n

4. A basic separator unit for assembly into a large area 'separator diaphragm vadapted for installation between the active-elements of a fuel combustion typeA of 7primary electrom'otive source comprising a thin flat rectangular tile Lhaving two comparativelylarge rectangular Yfacesu'rfaces Vand four comparatively small rectangular Vedge surfaces, fsaidtileeonsistingof 80 'partsby weight'of achemically inertjller material taken fromV the group consisting of talc, alumina, zirconia Vand beryllia, l0 partsby'weight ofbarium carbonate, .lparts by weight of a Asuitable high Vtemperaturel resisting ceramic clay, 11/2 parts by "weight of a suitable heavy bodied hydrocarbon emulsion, V4'and ll/zpartsby weight of graded corn meal, said tile beingprovided Ywith two apertures coaxial and coextensive with the two axes of said tile lying parallel to saidrectangular face surfaces thereof.

5. Aseparative diaphragm for separating the active -elements in yfuel combustion primary electric batteries A comprising a plurality of small rectangular-.tile-like units Y arranged in edge-to-edge relationship to forml a'relatively large Vthin rectangular flexible platev wherein each of said VVtile-like units consists of a Vthin rectangular `blocl: of

' porous,'high-compressive-strength ceramic materials having' two comparatively large rectangular faces and four comparatively small rectangular edges, saidv block vbeing lprovided with twoV apertures formedr coaxially and Vc0- Qexte'nsively with two of the principal axes ofsaidtblock,

said axes being parallel to said rectangularu faces, said units beingV arranged with said apertures in alignment `tl'fewhereby a plurality of apertures throughout thefbreadth and length of said large thin rectangular exible plate is formed;4V Vand elastic means threaded through said Vapertures for securing said units in said edge-to-edge relationship.

6. A separative diaphragm as claimed in claim 5 further characterized by said tile-like units comprising a formed thin rectangular block of high compressive strength porous ceramic materials Consisting of 80 parts by weight of talc, 10 parts by weight of barium carbonate, 10 parts by weight of high temperature resisting ceramic clay, 11/2 parts by weight of pitch and 11/2 parts by weight of mesh-graded corn meal, said materials being intimately mixed and said block being formed from said materials under one application of high pressure and high temperature to produce a block having great compressive strength and dimensional stability.

References Cited in the file of this patent UNITED STATES PATENTS Kendall Nov. 23, 1886 Flanders Apr. 19, 1904 Decker Aug. 11, 1908 McBerty Ian. 19, 1932 Crowley et al Aug. 14, 1945 Varela Apr. 25, 1950 Kock Feb. 12, 1957 Fischback et al. Feb. 9, 1960 

2. A BASIC SEPARATOR UNIT FOR ASSEMBLY INTO A LARGE AREA SEPARATOR ADAPTED FOR INSERTION BETWEEN THE ACTIVE ELEMENTS OF A FUEL COMBUSTION TYPE OF PRIMARY ELECTRIC BATTERY COMPRISING A THIN PARALLELEPIPED HAVING TWO PRINCIPAL FACES IN THE FORM OF RECTANGULAR PARALLELOGRAMS AND FOUR THIN EDGE ALSO IN THE FORM OF RECTANGULAR PARALLELOGRAMS, SAID PARALLELEPIPED BEING COMPOSED OF 80 PARTS BY WEIGHT OF TALC, 10 PARTS BY WEIGHT OF BARIUM CARBONATE, 10 PARTS BY WEIGHT OF CERAMIC CLAY 1 1/2 PARTS BY WEIGHT OF AN HYDROCARBON EMULSION AND 1 1/2 PARTS BY WEIGHT OF SUITABLY MESH GRADED CORN MEAL AND HAVING TWO APERATURES FORMED THEREIN, SAID APERTURES BEING COAXIAL WITH THOSE AXES OF THE PARALLELEPIPED WHICH ARE PERPENDICULAR TO THE OPPOSED EDGES THEREOF AND PARALLEL TO THE PRINCIPAL FACES THEREOF; 